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Infant directed speech produced by adolescent mothers varying in self-reported symptoms of depression

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Infant directed speech produced by adolescent mothers varying in self-reported symptoms of depression acoustic analysis and effects on infant associative learning
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Hoff, Ahna L
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English
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67 leaves : ; 28 cm

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Subjects / Keywords:
Paired-association learning ( lcsh )
Speech perception in infants ( lcsh )
Teenage mothers ( lcsh )
Mother and infant ( lcsh )
Children of depressed persons ( lcsh )
Children of depressed persons ( fast )
Mother and infant ( fast )
Paired-association learning ( fast )
Speech perception in infants ( fast )
Teenage mothers ( fast )
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bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

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Bibliography:
Includes bibliographical references (leaves 53-67).
General Note:
Department of Psychology
Statement of Responsibility:
by Ahna L. Hoff.

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|University of Colorado Denver
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|Auraria Library
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
40462408 ( OCLC )
ocm40462408
Classification:
LD1190.L645 1998m .H64 ( lcc )

Full Text
Infant Directed Speech Produced by Adolescent Mothers Varying in
Self-Reported Symptoms of Depression: Acoustic Analysis and
Effects on Infant Associative Learning
by
Ahna L. Hoff
B.S., Colorado State University, 1993
A thesis submitted to the
University of Colorado at Denver
in partial fulfillment
of the requirements for the degree of
Masters of Arts
Psychology
1998


This thesis for the Master of Arts
degree by
Ahna Luise Hoff
has been approved
by
Peter S. Kaplan
July 13, 1998
Date


Hoff, Ahna Luise (M.A., Clinical Psychology)
Infant Directed Speech Produced by Adolescent Mothers Varying in Self-Reported
Symptoms of Depression: Acoustic Analysis and Effects on Infant Associative
Learning
Thesis directed by Professor Peter S. Kaplan
Abstract
Infant directed (ID) speech segments produced by 19 adolescent mothers who
varied in self-reported symptoms of depression were recorded, edited into 10-s
speech segments, and presented to 190, 4 month-old infants of non-depressed
mothers. ID speech segments were used as conditioned stimuli that were paired
with face reinforcers to assess their ability to increase looking time at a novel
checkerboard pattern. Acoustic analysis indicated that the changes in frequency
modulation of the adolescent mothers voice was associated with the BDI score of
the mother who produced the speech segment. However, difference scores, a
measure of associative learning, were not correlated with BDI scores of the mother
who produced the speech segment or with changes in frequency modulation. In
addition, ID speech of adolescent mothers overall tends to be less modulated than
the ID speech of adult mothers. These results indicate that the quality of ID speech
may be influenced by age of the mother and depressive symptomology.
in


This abstract accurately represents the content of the candidates thesis. I
recommend its publication.
Signed
IV


DEDICATION
This Masters thesis is dedicated to my parents and my brother Eric
without whom I would have never have been able to accomplish my goals.


ACKNOWLEDGMENTS
A special thanks to Patricia Zarlengo-Strouse, Suzie Kleck and Carley
Pavelka for their constant support, encouragement and extremely hard work. Also
thanks to a wonderful mentor and teacher, Dr. Peter Kaplan for his endless
patience.


CONTENTS
IAPTER
INTRODUCTION.............................................................1
Adolescent Mother-Infant Interactions and Effects on Child Development.... 2
Adolescent Maternal Depression.....................................8
Adult Maternal Depression.........................................11
Infant Directed Speech.......................................... 13
Conditioning of Attentional Responses in Human Infants.....15
Infant Directed Speech of Adult Mothers....................17
Infant Directed Speech of Adolescent Mothers...............21
:. METHODS................................................................23
Participants......................................................23
Mothers....................................................23
Infants....................................................24
Infant Testing Apparatus..........................................25
Maternal Assessments..............................................25
Procedure.........................................................28
Dyadic Interactions.........................................28
Conditioned Attention..................................... 28
Acoustic Analysis...........................................30
RESULTS...................................................................31
Acoustic Analysis............................................... 31
vii


Conditioned Attention....................................33
Pairing Phase..................................... 33
Summation Phase.....................................34
. DISCUSSION....................................................38
PENDIX
A FIGURE.......................................................47
J. TABLES.......................................................48
3FERENCES.......................................................53
viu


CHAPTER 1
INTRODUCTION
The problem of adolescent pregnancy is a significant one, with high human
and economic costs to society. In 1988, 11% of American women between the
ages of 15 and 19 became pregnant, and these pregnancies accounted for 23.5% of
all births in the United States (Charles Stuart Mott Foundation, 1988). In 1990,
over one million teenagers became pregnant, and over one-half million of them
gave birth (Alan Guttmacher Institute, 1994). Although the rate of adolescent
motherhood in the United States has decreased in recent years, it is still twice as
high as that of the next highest industrialized nation (United Kingdom; Coley &
Chase-Lansdale, 1998).
Adolescent pregnancy and motherhood often present serious personal,
social, educational and professional challenges to a young mother that put her at
risk for long term problems including low educational attainment (Card & Wise,
1981; Furstenburg, Brooks-Gunn, & Chase-Lansdale, 1989; Hayes, 1987;
Osofsky, Osofsky, & Diamond, 1988; Roosa & Vaughn, 1984; Vukeluck &
Kliman, 1985), social isolation (Samuels, Stockdale, & Crase, 1994), low self-
esteem (Card & Wise, 1981; Furstenburg et al., 1989; Hayes, 1987; Osofsky et al.,
1988; Samuels et al., 1994), and economic disadvantage. Each of these adverse
outcomes, in turn, is known to be a risk factor for poor cognitive, emotional, and
1


social outcomes in the children of adolescent mothers (see below), and low socio-
economic status (SES) is associated with parental abuse and neglect (Zuravin,
1988). Although associations have been established between adolescent
motherhood and at-risk status of their children, little work has addressed the
question of the mechanisms by which adolescent mothers compromise their
children. The focus of the current work is how deficits in early adolescent mother-
child interactions, specifically the quality of stimulation provided by the mother to
the child, adversely affect infant learning. Before developing the specific
hypotheses that are the subject of the current thesis, however, some background
information on adolescent motherhood and consequences for infant and child
development are reviewed.
Adolescent Mother-Infant Interactions and Effects on Child Development
A growing body of evidence has shown that caregivers play a central role
in regulating their infants state of arousal and affect, mainly through repetitive and
rhythmic vocal, facial, gestural, kinesthetic and tactile stimulation (Stem, Bebee,
Jaflfe & Bennett, 1977; Stem, Bebee, Jaflfe & Bennett, 1975). Caregivers sustain
high infant attention and positive affect using, for example, exaggerated vocal
intonations and facial expressions (Cohn & Tronick, 1987). Both the quality of
such stimulation and the degree of synchronization between caregiver and infant
behavior have been shown to be keys to successful dyadic interactions (Cohn &
2


Elmore, 1988; Kaplan, Bachorowski & Zarlengo-Strouse, in press; Tronick,
1982). Importantly, the quality of early caregiver-infant interactions is associated
with the quality of later mother-child attachment, child affect regulation and child
cognitive development. There is evidence to suggest that there may be disruptions
or deficits within adolescent mother-infant interactions in particular and it is this
evidence which is addressed in the below.
Adolescent mothers have been found to be more punitive, more
authoritative, and to have less realistic expectations for their infants than adult
mothers (Camp, 1995; Field et al. 1980; Kissman, 1988; Reis & Hertz, 1987).
Adolescent mothers with more punitive child-rearing attitudes have less realistic
expectations of their infants and less optimal evaluations of their infants
temperaments than do their adult counterparts (Field et al., 1980). Importantly in
the current context, adolescent mothers spend less time talking to (Culp,
Applebaum, Osofsky & Levy, 1988; Field et al., 1990; Lester & Zeshin, 1978) and
looking at their infants (Osofsky et al., 1988), and are more affectively negative
toward their infants (Culp et al., 1988, Barrat & Roach, 1995; Leadbeater, Bishop
& Raver, 1996) than are adult mothers. According to McAramey and Lawrence
(1979), the younger the mother, the less likely she is to exhibit touching,
synchronous movement, physical closeness, and a high-pitched voice in
interactions with her infant. Barratt and Roach (1995) showed that adolescent
3


mothers vocalized significantly less, offered or showed toys less, and smiled less to
their four-month-old infants than did adults. Infants of adolescent mothers
correspondingly vocalized and smiled less than did the infants of adult mothers.
Thus, to the extent that the failure of withdrawn caregivers to provide needed
response-contingent stimulation to their infants affects infant behavior and places
infants at risk for later behavioral and psychological problems, the infants of
adolescent mothers may be expected to be particularly at risk.
Studies on physical and cognitive development in infants of adolescent
mothers have turned up a number of adverse consequences, but pinpointing the
causes of these consequences has been difficult. For example, early research
suggested that the infants of adolescent mothers were at greater risk for physical
health problems such as lower birth weight and greater incidence of perinatal
mortality. However, recent research reveals that once factors such as SES,
legitimacy status, and perinatal care are controlled, the infants of adolescent
mothers fare as well as the infants of adult mothers (Baldwin & Cain, 1980;
McAramey and Thiede, 1981). Children bom to mothers under the age of 15, who
have lower birth weight than children of older adolescents or adults, seem to be the
exception to this rule (Ketterlinus, Henderson and Lamb, i990).
With respect to emotional development, Marecek (1979) used observations
taken during the administration of IQ tests along with reports from caregivers at
4


four and seven years of age to show that maternal age had little effect on child
emotional development at four years, but that by seven years children of mothers
under 18 years of age at the time of the childs birth displayed more overactivity,
hostility, restiveness and impulsiveness. However, findings from this study must
be interpreted with caution due to a lack of control over SES and race.
Examining the results from Bayley and IQ tests, Marecek (1979) reported
no differences in performance between infants and children of adolescent and adult
mothers in cognitive development at eight months and four years of age.
However, differences in scores on the Weschler Intelligence Scale for Children
(WISC) were evident at seven years of age, with the boys of adolescent mothers
scoring significantly lower than the boys of adult mothers on verbal comprehension
and expression and performance (manipulation of concrete materials and visual
motor activities) scales. Further evidence for adverse cognitive development
effects of adolescent motherhood comes from a study by Furstenburg (1976)
showing that scores of 42 to 60 month-old children of low income urban black
adolescents on the Preschool Inventory (PSI) tended to be negatively correlated
with the amount of time the adolescent mother spent with her child.
Field et al. (1990) carried out a longitudinal assessment of Bayley Scale
performance in 12-, 18-, and 24-month-old infants of Cuban and African-American
adolescent mothers in Miami. They found a steady decrease in scores on the
5


Bayley Mental Scale as a function of age. Relative to age norms, infants of
adolescent mothers exhibited a decrease in language production between 12 and
24 months. The decrease in Bayley scores from 12 to 24 months were correlated
with a decrease in maternal play behavior between 12 and 18 months.
Evidence suggests effects on school performance of adolescent
motherhood. Furstenburg et al. (1989) found that one-half of the children of
African-American adolescent mothers had failed a grade, relative to only 20% of
the children bom to later African-American child bearers, as reported in the Nation
Survey of Children. Ketterlinus, Henderson, and Lamb (1991) used data from a
national probability sample of households to examine maternal age at birth,
maternal intelligence, sociodemographic status and quality of the home
environment on childrens achievement. They concluded that three groups of
children were more likely to perform poorly on arithmetic and reading achievement
tests: children of mothers who did not provide a stimulating home environment,
children of mothers with low math and reading scores, and children of young black
mothers.
Poverty is strongly associated with adolescent motherhood (Klerman,
1993; McLoyd, 1998). Poverty and lack of prenatal care are directly associated
with negative health outcomes for infants and mothers, including premature birth,
low birth weight, and perinatal complications (Klerman, 1993; McLoyd, 1998;
6


Scholl, Hedger & Belsky, 1994). Studies that controlled for maternal IQ,
education, age, and behavior during pregnancy report significant effects of poverty
on childrens cognitive and verbal skills (Korenman, Miller & Sjaastad, 1995; Liaw
& Brooks-Gunn, 1994; Smith, Brooks-Gunn & Klebanov, 1997), suggesting that
poverty and not adolescent mother status itself may be the main causal factor. The
children of adolescent mothers may not necessarily be at risk due to the age of
their mother but may be at high risk for developmental problems because their
mothers are more likely to be poor than the children of adult mothers.
Adolescent mothers represent a group of mothers who are not only
themselves at risk for psychological, social, educational and economic
disadvantage but who also place their infants at risk for adverse developmental
outcome. In face-to face interactions with their infants, adolescent mothers are
more likely to be withdrawn, to exhibit negative affect toward their infants, and to
have punitive child rearing habits and unrealistic expectations. In addition, they
are less likely to touch and smile at, verbally stimulate, direct contingent responses
toward, play with, and maintain close physical proximity with their children. They
are also more likely to experience significant symptoms of depression than either
age- and gender-matched peers or adult mothers. The infants of adolescent
mothers are in turn, at risk for physical, emotional, and cognitive developmental
7


problems although many of these problems may be attributed to correlates of
adolescent motherhood, especially low SES.
Adolescent Maternal Depression
There are other sequelae to adolescent mother status that may be expected
to adversely affect parenting behavior and child development (see below). One
such factor is mood disturbance. Between 13 and 34% of non-childbearing
adolescents report moderate levels of symptoms associated with depression. Five
to eight percent of these adolescents meet DSM-III-R or DSM-IV Axis-I
diagnostic criteria (Gibbs, 1985; Kandel & Davies, 1982; Kashani et al., 1987;
Leadbeater & Linares, 1992; Oz et al., 1992). The cognitive features of depression
in adolescents parallel those in adults. Hammond and Romney (1995) found that
depressed adolescents reported a greater discrepancy between their perceived self
and ideal self. Depressed adolescents also perceived themselves as more socially
isolated and unlike other people, and exhibited more hopelessness, more
dichotomous thinking (black or white thinking), and high levels of external locus
of control relative to somewhat depressed and nondepressed controls.
Through an extensive literature review, Leadbeater, Blatt and Quinlan
(1995) concluded that female adolescents are more likely to experience depressive
feelings, suicidality and eating disorders. They also concluded that females were
more affected by interpersonal depressive vulnerabilities, that is, depressive
8


vulnerabilities where the individual tends to be more reactive to stressful life events
which involve others.
Adolescent mothers report a higher percentage of depressive symptoms
than do other non-parenting adolescents or adult mothers. Thirty to 59% of
adolescent mothers report moderate to severe levels of depression (Colleta, 1983;
Zuckerman, Amaro & Beardslee, 1987). Depressed teenage mothers experience
more psychosocial stressors than non-mothering peers, more physical health
problems, more mental health probleriis, poorer family and peer relations, and
decreased vocational and social skills (Prodromidis et al., 1994). Single mothers
who have not completed high school and who are between the ages of 14 and 17
are even more likely to experience depression (Leadbeater & Linares, 1992).
Adolescent mothers tend to be more susceptible to depression when faced with
high levels of interpersonal stress (e.g., difficulties with partner or spouse),
consistent with their increased susceptibility to interpersonal depressive
vulnerabilities.
Research suggests that adolescent maternal depression is long lasting.
Leadbeater & Linares (1992) found that self-reports of depression in 120-inner-
city adolescent mother tended to remain high in 70% of the mothers between six
and 12 months post-partum and in 65% of the mothers between 28 and 36 months
post-partum. Although the number of symptoms associated with depression
9


decreased over the three-year span of the study, this decrease was attributable
entirely to a reduction in the number of reported somatic symptoms. Reports of
cognitive symptoms remained constant throughout the study.
As will be reviewed in more detail in the following, maternal depression is
known to have an adverse impact on adult mother-infant interactions, and to
significantly increase the infants risk for later problems in attachment, affect
regulation, and cognition. However, little is known about the impact of depression
in adolescent mothers on dyadic functioning and infant development. Leadbeater
et al. (1996) studied 63 adolescent mothers and their first bom children to examine
the relationship between maternal depressive symptoms, dyadic reciprocity, and
child behavior problems. They hypothesized that depressive symptoms, mother-
child conflict, and contingent responses would all be predictive of behavior
problems. They found that greater mother-child conflict at 20 months of age
predicted further problem behaviors at 28 to 36 months, as did maternal depressive
symptoms. Furthermore, depressive symptoms were significantly related to
contingent responses. For further insight into the effects of maternal depression on
the functioning of the mother and her child, studies examining effects of adult
maternal depression will now be reviewed.
10


Adult Maternal Depression
Approximately eight to 10 percent of new adult mothers are clinically
depressed (Weissman, Leaf, & Bruce, 1987; OHara, Neunaber, & Zekoski,1984).
Depressed individuals when engaging in adult directed (AD) speech speak less
than controls (Aronson and Weintraub, 1972; Kanfer, 1960), have slower rates of
speech (Teasdale, Fogarty, & Williams, 1980), differ in vocal quality (Scherer,
1986), and display disruptions in emotional expressiveness and responsiveness
(Lewinsohn, Weinsten & Alper, 1970; Libert and Lewinsohn, 1973). Vocal
interactions of depressed mothers with adults contain more sad and angry content
than non-depressed controls (Breznitz, 1992; Field, Healy, Goldstein and Guthertz,
1990).
Likewise, depression influences the mother-child dyadic interaction. As a
group, depressed mothers express less positive affect during interactions with their
two month-old infants than non-depressed mothers (Cohn, Campbell, Matiais and
Hopkins, 1990). Depressed mothers also tend to be more irritable during
interactions with their infants than are control mothers (Cohn et al., 1990; Field,
1984). They express greater negativity towards the demands of parenthood
(Cohn, Cambell, Matias, and Hopkins, 1986; 1990; Field 1984) and feelings of
hostility and rejection toward their child than non-depressed controls (Breznitz,
1992; Colletta, 1983). Depressed mothers view the role of parent less positively
11


and perceive themselves as less competent than do control mothers (Davenport,
Zahn-Waxler, Adland & Mayfield, 1984; Webster-Stratton and Hammond, 1988).
The conversational structure of the mother-infant interaction depends on
the mothers ability to respond to the infant in an appropriate manner temporally,
responsively and physically. Temporally, depressed mothers respond less quickly
and less spontaneously. Depressed mothers are generally less vocally responsive
(Breznitz and Sherman, 1987), and respond less consistently and contingently
(Field et al., 1988). They also tend to be more physically distant when playing
with their infants than control mothers (Bettes, 1988; Breznitz and Sherman, 1987;
Cohn, Matias, Tronic, Connell and Lyons-Ruth, 1986; Field et al., 1985; Field,
1984).
The interaction between a mother and her infant is a reciprocal one and
can be observed at a very young age. Two- to three- month-old infants match
their mothers positive and negative affect during face to face interactions
(Hammen, Gordon, Burge, Adrian, Jaenicke and Hirolo, 1987; Cohn and
Campbell, 1992). Children of depressed mothers direct their behavior toward their
mother less frequently, smile and express happiness less frequently and tend to be
more irritable and fussy than infants of non-depressed mothers (Cohn et al., 1986;
1990; Field, 1984; Field, Sandburg, Garcia, Vega-Lahr, Goldstein & Guy, 1985;
Lyons-Ruth, Zoll, Connell, Grunebaum, 1986). Infants of depressed mothers are
12


also less attentive and less active (Field et al. 1988). The interactional styles of
infants of depressed mothers are maintained even when interacting with non-
depressed female strangers (Field et al., 1988), suggesting that the mother and
child may contribute equally to interactional patterns (Cohn et al.,1990; Field et
al.,1990).
Maternal depression has also been shown to affect the emotional
development of the child. Children of depressed mothers have higher rates of
insecure attachment evidenced by avoidance and disorganized and disoriented
behaviors (Murray, 1992). Forty-seven percent of the two-to-three year old
children of mothers with Major Depressive Disorder show evidence of insecure
attachment as compared to 25 to 30 percent in the control group and in minor
depression groups (Radke-Yarrow, Cummings, Kuczynski, & Chapman 1985).
Moreover, Downey and Coyne (1990), in reviewing the results of nine studies,
found that children of depressed (uni-polar) parents were at heightened risk for
affective disorders, with a rate of Major Depressive Disorder six times higher than
that of control children.
Infant Directed Speech
The vocal channel of stimulation, more specifically the unique qualities of
infant directed (ID) speech, have been shown to be particularly important in
mother-infant interactions. Acoustically, ID speech is characterized by higher
13


overall fundamental frequency (F0, a strong acoustic correlate of vocal pitch),
exaggerated change in Fo, greater Fo variability and greater amplitude modulation
than is AD speech (Femald, 1984; Femald & Simon, 1985). In addition, ID
speech tends to have a slower tempo, longer pauses between words, simplification
of vocabulaiy and syntactic structure, and more repetitionsall adaptations to
increase infants responsiveness (Jacobsen, 1983; Snow, 1972).
The unique acoustic, temporal, and linguistic properties of ID speech are
thought to promote stronger attentional and behavioral responding in infants
(Cooper and Aslin, 1980; Femald, 1985; Femald and Kuhl, 1987; Kaplan et al.
1996; Werker, & McLeod, 1989). Femald (1984) posited that ID speech more
effectively recruits and maintains infant attention, modulates infant affect and state
of arousal, and facilitates the processing of information relative to AD speech. A
large body of evidence points to stronger effects of ID than AD speech on
attracting and maintaining infants attention (Cooper and Aslin, 1990; Femald,
1985; Femald and Kuhl, 1987; Kaplan, Goldstein, Huckeby, Owren, & Cooper
1995; Pegg, Werker, & McLeod, 1992) and modulating infant affect and arousal
(Femald, 1985; Kaplan et al.,1995). In addition, recent evidence gathered at the
Infant Perception Laboratory at the University of Colorado at Denver point to
effects of ID speech on a basic form of information-procession in young infants.
14


Because that work forms the basis for this project, it will be reviewed in detail in
the following sections.
Conditioning of Attentional Responses in Human Infants
A simple procedure for studying the formation of audio-visual associations
was developed by Kaplan, Fox & Huckeby (1992). They devised a 5 min test with
independent groups of four month-old infants. In the pairing phase, the forward
pairing group of infants was presented with six forward pairings of a 10-s, 65 dB,
1000 Hz, square wave tone (conditioned stimulus or CS) that was followed
immediately by a 10-s photographic slide of a smiling adult female face
(unconditioned stimulus or UCS). Three control groups of infants received either
the same two stimuli but in reversed order (backward pairings), the same two
stimuli presented randomly with respect to one another (random control) or only
the face stimulus. In the summation test phase, all groups of infants were given
four 10-s presentations of a novel 4X4 black and white checkerboard pattern, with
10-s interstimulus intervals (ISIs) between each checkerboard presentation. The
tone from the pairing phase was presented simultaneously with the first and fourth
checkerboard, whereas the second and third were presented in silence, (in a second
experiment, test trial order was counterbalanced, with no significant effect on
performance). The main dependent measure was the duration of looking at the
projection screen during presentations of the tone. The primary finding was that,
15


although there were no differences in looking at the projection screen during tone
presentations in the pairing phase, infants in the forward pairing group only looked
significantly more at the checkerboard pattern during tone presentations vs. in
absence of tones (positive summation). Because the ability of tones to increase
looking at checkerboard presentations depended on prior forward pairings of tone
and face, it was concluded that the positive summation observed was due to an
associative effect, i.e., that it reflected the infants learning that the tone predicted
face presentations.
Kaplan, Jung, Ryther & Zarlengo-Strouse (1996) adapted this paradigm to
study the relative effectiveness of ID vs. AD speech segments as signals for the
face reinforcer1. In four independent groups, both forward and backward pairings
of ID and AD speech segments with the smiling face reinforcer were investigated.
Results showed that, again, there were no group differences in responding to
speech segments or faces during the pairing phase. Only when an ID speech
segment was presented in a forward pairing arrangement with the face reinforcer
did significant positive summation occur. Neither forward nor backward pairings
of the AD speech segment and face produced any effect on the ability of the AD
speech to increase looking at the checkerboard pattern (suggesting that perhaps
infants were predisposed not to attend strongly to AD speech).
16


As mentioned above, specific acoustic properties of ID speech are thought
to make it more effective at eliciting infant responding than is AD speech.
Exaggerated frequency (F0) modulation is posited to be an important determinant
of the effectiveness of ID speech by gaining infant attention, increasing infant
arousal (Femald, 1984; Femald and Kuhl, 1987) and responsiveness (Cooper and
Aslin, 1994; Kaplan et al., 1995).
Literature on ID speech clearly indicates that ID speech is an important
medium through which caretakers regulate infant state and attention as well as
direct the infants attention to relevant features in the environment. However, few
studies have addressed disruptions in the production of ID speech and the effects
these disruptions may have on the dyadic process. The following addresses the
effects of disruption in the production of ID speech caused by changes in maternal
affective states.
Infant Directed Speech of Adult Depressed Mothers
The AD vocalizations of depressed individuals have lower minimum and
maximum Fo, lower mean Fo values, and smaller Fo range (Nilsonne, 1987; Alpert,
1982). Similar qualities are observed in the AD speech of depressed mothers
including a narrow range of Fo and longer pauses between vocalizations (Breznitz,
1993). Given that exaggerated frequency modulated contours facilitate infant
attention, these deficits in speech production could have an effect on the ability of
17


the mother to effectively maintain her infants attention (Stem et al., 1982;
Papousek, Papousek and Symmes, 1991; Kaplan and Owren, 1994; Kaplan,
Bachorowski and Zarlengo-Strouse, in press). However, contrary to what might
be expected, mothers did not exhibit differences in the amount of speech
production or mean length of utterance relative to non-depressed mothers
(Murray, Kempton, Woolgar, and Hooper, 1993; Radke-Yarrow et al., 1990).
However, another study points to some differences in ID speech produced
by mothers who varied in self-reported symptoms of depression. Bettes (1988)
studied two min maternal speech segments produced during play interactions of
mothers reporting various symptoms of depression on the Beck Depression
Inventory (BDI). Bettes divided the mothers into two categories: non-depressed
(BDI < 10) and depressed (BDI > than 10). Mothers scoring in the moderate to
mild range of the BDI (BDI > than 10) produced fewer exaggerated F0 intonation
contours than mothers with BDIs lower than 10 (85% vs. 96%). In addition, the
depressed mothers produced fewer vocalizations with longer and more variable
latencies when responding to their infants vocalizations. The deficits exhibited by
the depressed mothers compared to the non-depressed mothers in this study,
including greater variability in the length of pauses and utterances, longer and more
variable latencies when responding to the infant, and less modulation, may put
these women at a disadvantage in their attempts to communicate with their infants.
18


However, Bettes (1988) did not examine the infants responses to ID
speech produced by the mothers in her study. Kaplan, Bachorowski and Zarlengo-
Strouse (in press) for the first time demonstrated that infants respond differently to
the quality of vocal stimulation produced by mothers varying in symptoms of
depression. In a conditioned attention study utilizing the paradigm described
previously, they compared the effects of varying vocal qualities of speech segments
produced by mothers varying in self-reported symptoms of depression (Kaplan et
al., 1992). During a structured play interaction mothers were asked to interest their
infant in a stuffed gorilla using the phrase pet the gorilla. The phrase pet the
gorilla was used as the ID speech segment to achieve a consistent vocal content.
Immediately following the recording session mothers were then assessed for
symptoms of depression with the BDI and the Structured Clinical Interview for the
DSM-IV (SCID; First, Spitzer, Gibbon, & Williams, 1995; Beck, 1970; Beck,
Ward, Mendelson, Mach, & Erbaugh, 1961).
Pet the gorilla phrases were then edited into 10-s speech segments used
in a conditioned attention task that consisted of a pairing and a conditioning phase.
Each 10-s speech segment consisted of three pet the gorilla phrases (two
interrogatives and one declarative) selected from the recording of the play session
The three pet the gorilla phrases were then repeated once. In the pairing phase
the infant was presented with a 10-s speech segment (CS) immediately followed by
19


a 10-s slide of a female smiling face (UCS). Each voice-face presentation was
separated by a 10-s ISI.
Results from the pairing phase of the study indicated no differences in
response to either the speech sample or smiling face as a function of the BDI
category of the mother who produced the speech segment. As in previous studies,
the measure of conditioning during the summation phase was the difference score
(Kaplan et al., 1992; Kaplan and Owren, 1994). Kaplan et al. (in press) found that
the infants conditioned attention performance differed as a function of the BDI
score of the mother who provided the speech sample. Significant conditioning
occurred using speech segments produced by mothers with fewer self-reported
symptoms of depression, whereas no conditioning was evident using speech
segments produced by mothers with comparatively more symptoms of depression
(and DSM-IV Axis-I diagnosis).
Speech acoustics for all of the BDI groups were also analyzed by Kaplan et
al. (in press). Eighty-six percent of the fundamental frequency contours of the
gorilla utterance in the high BDI condition were classified as unmodulated as
compared to 33 % in the middle BDI group and zero percent in the low BDI
group. Each 10-s speech segment consisted of three pet the gorilla phrases (two
interrogatives and one declarative) repeated once. Analysis of the third gorilla
utterance of the pet the gorilla phrase indicated significant negative correlations
20


between BDI category and extent of the categorical F0 change (using a 150 Hz
criterion).
Infant Directed Speech of Adolescent Mothers
Adolescent mothers represent a distinct population of mothers faced with a
unique set of circumstances and risk factors which put them at risk for depression.
As described, Kaplan et al. (in press) demonstrated that ID speech produced by
adult mothers who reported relatively more symptoms of depression failed to
promote associative learning as effectively as the ID speech produced by adult
mothers reporting relatively fewer symptoms of depression. Yet, up to this point
no one has explored the effects that these risk factors and circumstances may have
on the adolescent mothers ability to produce infant directed speech. Therefore,
here, for the first time the acoustic qualities of the infant directed speech of
adolescent mothers will be examined. In addition, because depression has been
shown to affect adult mothers ID speech, and because adolescent mothers are
thought to be at relatively higher risk for depression, the effects of depression of
the ID speech of the adolescent mother will be examined.
As in the Kaplan et al. (in press) study, the speech segments will be
categorized and analyzed according to the BDI score of the mother who produced
the speech segment (Independent Variable; IV). The variables being measured, or
the dependent variables (DVs), will be the mean Fo, the mean change in Fo and the
21


conditioning scores of the infants presented with the speech samples. Therefore, in
the following study it is predicted that the BDI score and depressive symptoms
reported by the mother will be correlated with changes in the acoustics of the
mothers ID speech and consequently the conditioning scores obtained from the
infants presented with the voice of the mother. Since Kaplan et al. (in press) found
that there were significant acoustic differences among BDI scores in the gorilla
portion of the speech segment, particular attention will be focused on the gorilla
utterance, with the expectation that it will be less modulated in higher BDI
categories. Although this is the first study to specifically examine the ID speech of
adolescent mothers, differences between the ID speech of adolescent and adult
mothers are expected as differences in the dyadic interactions of adult and
adolescent mothers with their infants have been demonstrated.
22


CHAPTER 2
METHOD
Participants
Mothers
Twenty-four mother-infant dyads were recruited through school- based
programs or local clinics specializing in the treatment of adolescent mothers.
Flyers were distributed at six local clinics that specialized in the treatment of
adolescent mothers. It is unknown how many mothers viewed these flyers. One
clinic obtained permission from their clients and released addresses of 40 mothers
and recruitment letters were sent to eligible mothers. Five min presentations were
presented at five school-based programs and four birthing or parenting classes to
approximately 155 mothers. Following each presentation mothers were given a
copy of a recruitment flyer and given an opportunity to sign-up to receive further
information about the study. Of the approximately 195 mothers directly contacted
through letters or presentations, 50% signed up and of those 24.5% were eligible
and willing to participate.
Five of the mothers were excluded from analysis one due to their
membership in a distinct recruitment sample and four due to time constraints on
the study. Of the nineteen mothers studied, eight were non-Hispanic white, seven
were Hispanic and four were African-American. Their ages ranged from 14 to 18
23


years with an overall mean age of 16.42 years. All of the mothers were
primiparous. None of the mothers reported being on psychotropic medication.
Four of the mothers reported taking pre-natal vitamins, two mothers were on birth
control pills, one was on Depoprovara (a hormonal injection for birth control), one
had an inhaler for asthma and one was taking iron supplements.
One of the mothers had graduated from high school, one had obtained her
GED and the remaining 17 mothers had not completed high school. One mother
was married and the remaining were single. Sources of financial support varied
widely across mothers. Eight out of the 19 mothers studied lived outside their
family of origin either with a friend or boyfriend. Of these eight, one was on
welfare, tliree were unemployed and four were working in low wage service jobs
such as fast food service. Of those supported by their parents, seven were working
in low wage service jobs to supplement family income and to support their infant.
The remaining four were supported solely by their parents and chose not to work
at the time they were interviewed.
Infants
A self-selected sample of 214 healthy, full-term, four month-old infants of
adult non-depressed mothers were recruited through birth notices purchased from
the Bureau of Vital Statistics of the City and County of Denver. Letters of
recruitment explaining the study were sent to the parents and follow-up calls were
24


made to improve recruitment and to schedule appointments. Twenty-four of the
infants were excluded from final analysis due to excessive crying (n=9), equipment
failure (n=5), experimenter error (n=2), sleeping (n=2), not looking (n=2), or
prematurity (n=4). Of the one-hundred and ninety to be included in data analysis
89 were male and 101 were female. One hundred sixty-nine infants were non-
white Hispanic (79%), 14 were Hispanic (7.5%), four were African-American
(2%), two were Asian (1%) and one was Native American (0.5%).
Infant Testing Apparatus
Infants were seated in a standard car seat reclined to a 70 angle in front of
a 10.8 cm square translucent rear-projection screen centered within a vertically
standing, large flat-black wooden board. A video camera (Hitachi model
HV725U) was located 1.9 cm to the infants left of the screen which provided a
full face view of the infant that was displayed on two separate 19-in black and
white Panasonic video monitors (Model WV-5470). Voices were presented on a
JBL control-1 loud speaker located 10 cm below and 33.5 cm behind the infants
head.
Maternal Assessments
Maternal depressive symptoms were assessed using the Beck Depression
Inventory (BDI; Beck, Ward, Mendelson, Mach, Erbaugh, 1961), the Reynolds
Adolescent Depression Scale (RADS; Reynolds, 1987), and the Structured Clinical
25


Interview for the DSM-IV Axis I diagnosis (First, et al., 1995). The Beck
Depression Inventory is a 21-item self-report questionnaire which assesses
symptoms of depression. It has been widely used in clinical and non-clinical
samples of adolescents with satisfactory reliability and validity (Byrne, Baron, &
Campbell 1993; Kendall, Hollon, Beck, Hammen, & Ingram, 1987). In some
analyses presented below mothers were categorized by BDI scores as proposed by
Beck et al. (1961), where scores ranging between one and nine indicate non-
depressed, scores between 10 and 15 indicate mild mood disturbance, and scores
of 16 or above indicate borderline to moderate depression.
Beck Depression Inventory scores for the current sample of mothers
ranged from two to 25 (M = 11.2) with eight of the mothers scoring between 0
and 9 (low), eight scoring between 10 and 15 (mid), and three scoring 16 and
above (high). Of the women in the low BDI category: one was diagnosed with
a past Major Depressive Episode and Substance Dependence in full remission, one
was diagnosed with Substance Dependence in full remission, one was diagnosed
with Panic Disorder with Agoraphobia in partial remission and the remaining
received no DSM-IV Axis I diagnosis. In the mid BDI category one was
diagnosed with a Major Depressive Episode, one was diagnosed with Post
Traumatic Stress Disorder and Substance Dependence in full remission, another
had specific phobias and the remaining had no DSM-IV Axis I diagnosis. In the
26


high BDI category one was experiencing a Major Depressive Episode, one
dysthymia, and one had a past Major Depressive Episode.
The RADS is a 30-item self-report questionnaire that has been widely used
in non-clinical samples of adolescents and has been reported to have satisfactory
reliability and validity (Davis, 1990; Reynolds, 1987). Scores on the RADS range
from 30 to 120, with higher scores indicating greater levels of disturbance. RADS
manual cites a cutoff score of 77 and above to delineate a level of symptom
endorsement associated with clinical depression. RADS scores ranged from 36-
72 with an average score of 53.3.
The Structured Clinical Interview for the DSM-IV Axis I diagnosis (First
et al.,1995) assesses past and present occurrences of mental illness. All interviews
were conducted by the author who was a graduate student enrolled in the Clinical
Psychology Masters Degree program, supervised by advanced graduate students
and the Director of the Clinical Psychology training program at the University of
Colorado at Denver, Dr. Michael Zinser. Training involved repeated role playing
experiences and observation of the trainer by the student and the student by the
trainer. The interviews lasted approximately one to one and a half hours.
27


Procedure
Dyadic Interactions
Mothers and their infants interacted in a structured play session during
which the mother was asked to interest her infant in a stuffed gorilla using the
/
phrase pet the gorilla. The mother was asked to interest her infant in the toy to
encourage attentional rising F0 contours (Kaplan & Owren, 1994; Papousek, 1991;
Stem et al., 1982) while the speech segment pet the gorilla was used to elicit
consistent linguistic content across all mothers. A Digital Audio Tape recorder was
used to record the mothers voice through a Lavaliere lapel microphone that was
attached to the mothers shirt collar. Recordings were edited with a Macintosh
Quadra Computer using Sound Edit 16 bit software with 16 bit resolution and a 44
kHz sampling rate. The first two interrogatives and the first declarative pet the
gorilla phrases were isolated from the original recording and then combined into a
single speech segment. Each speech segment was repeated once yielding six pet
the gorilla phrases for a total stimulus duration of 10 seconds.
Conditioned Attention
Ten four-month-old infants were randomly assigned to each of 19
treatment conditions defined by the BDI score of the mother who provided the
speech sample. During the pairing phase the infant received six-10 second
presentations of the pet the gorilla speech segment which was immediately
28


followed by a 10-s achromatic photographic slide of a Caucasian adult female
smiling face. Between each presentation there was an ISI of 10-s (blank slide).
The pairing phase was immediately followed by the summation test phase in which
each infant received four presentations of a 10-s 4X4 black and white
checkerboard pattern. The speech segment from the pairing phase was presented
concurrently with the first and fourth presentations of the checkerboard. The
second and third presentations of the checkerboard occurred in silence.
The dependent variable was the length of looking time during each 10-s
interval, which was measured using the corneal reflection technique. The corneal
reflection technique is a process by which a primary and secondary observer press
down on a hand held switch when the reflection of the image is centered on the
infants pupil. The primary observer was naive to the BDI score, SCID diagnosis
and age of the mother who produced the speech sample, and could not see or hear
the stimulus being presented. The second observer was in a separate testing room
with the infant and could not see the primary observer. The second observer was
responsible for running the equipment that presented the stimulus to the infant and
was therefore not naive to the treatment condition. The mean inter-observer
correlation was r = .92 (Range = .71-1.0).
29


Acoustic Analyses
Acoustic analyses were carried out with the assistance of Dr. Jo-Anne
Bachorowski of Vanderbilt University. Tape recorded pet the gorilla speech
segments were digitized at 50 IcHz with 16-bit resolution and analyzed using the
Computerized Speech Lab Model 4300B (Kay Elemetrics, Lincoln Park, NJ).
Mean Fo, change in Fo and contour classification using a 150 Hz criterion were
used in analysis because these acoustic properties have been shown to be an
important characteristic of ID speech (Femald and Simon, 1994; Katz et al., 1996,
Papousek et al., 1991) and because it tends to differ among mothers who vary in
self-reported symptoms of depression (Bettes, 1988, Kaplan et al. in press).
Analysis centered on the gorilla portions of the pet the gorilla utterances
because these portions were found to be affected by variations in self-reported
symptoms of depression in the Kaplan et al. (in press) study.
30


CHAPTER 3
RESULTS
Acoustic Analysis
Acoustic analysis focused on summary fundamental frequency (F0)
measures for each maternal gorilla utterance (Table 1). As can be seen, for both
mean F0 and mean change in F0, mean values decreased as the BDI score of the
mother who provided the speech sample increased. A bivariate correlation revealed
a significant association between the BDI score of the mother who produced the
speech segment and the mean F0 change in the gorilla portion of the utterance,
r(l 8) = 0.51, p < .03. Figure 1 plots the mean F0 change in the gorilla portion of
the utterance as a function of the BDI score of the mother who produced the
speech segment. There was also a significant bivariate relationship between mean
F0and mean change in F0 for gorilla utterances, r(18) = 0.54, p < .02, but no
significant relationship between BDI score and mean F0 (r(18) = 0.16, p = .55).
When these data were analyzed with one-way ANOVAs according to the three
BDI categories described above, there were no significant effects for mean F0 or
change in F0. (ps > .50).
The left panel of Table 2 presents durations, fundamental frequencies (F0s),
changes in F0, and percent of gorilla utterances that were classified as
unmodulated or flat (i.e., containing less than 150 Hz change in frequency, see
31


Kaplan et al., in press) for each of the three gorilla utterances produced by
adolescent mothers in each of the three BDI categories. The right panel presents
archival data for adult mothers from the Kaplan et al. (in press) study. Using age
groups (adult or adolescent) and BDI groups as grouping variables, a MANOVA
examined the mean F0 and mean change in Fo for all three pet the gorilla phrases.
Analyses revealed, relative to the adult mothers, adolescent mothers had a
significantly higher mean F0, F (1, 38) = 4.10, p = .05. In addition, in a separate
ANOVA yield, a significantly higher percentage of utterances were classified as
flat using the 150 Hz criterion,3 F(l,38) = 4.62, p = .04. For both adolescent
and adult mothers, mean F0 change decreased and the proportion of unmodulated
gorilla utterances increased as a function of the BDI score of the mother who
provided the speech sample. However, none of these trends in the adolescent
mothers data was statistically reliable.
There were also significant acoustic differences present depending on the
ethnicity of the adolescent mother who produced the speech sample. The mean
frequency change during the gorilla portion of the speech segment was 188.63
Hz (SD = 59.1), 103. 75 (SD = 41.27), and 104.29 (SD = 29.77) for the non-
Hispanic white, African-American and Hispanic groups respectively. A one-way
ANOVA demonstrated a significant effect on mean change in Fo for gorilla
utterances as a function of mothers ethnic group, F(2, 15) = 6.11, p < .02, and
32


subsequent Neuman-Keuls tests revealed significant differences between Caucasian
and African-American mothers and between Caucasian and Hispanic mothers (p <
.02). Similarly, there was a significant effect of maternal ethnicity on mean F0 for
gorilla utterances, F(2, 15) = 4.29, p < .04, and subsequent Neuman-Keuls
showed differences between Caucasian and African-American mothers and
Caucasian and Hispanic mothers but not between African-American and Hispanic
mothers.
Conditioned Attention
Pairing Phase
Infant directed speech produced by adolescent mothers who varied in self-
reported symptoms of depression was presented to infants of non-depressed adult
mothers. As in the studies described above, looking times at a uniformly
illuminated projection screen during the voice presentations were examined to
assess changes during the pairing phase as a function of the BDI category of the
mother who produced the speech segment, and as a function of the number of
times the infant was presented with the vocal stimulus. A one-way ANOVA found
no significant differences in looking times during the voice presentations as a
function of the BDI score of the mother who produced the speech sample
(F(2,187) = 1.40, p = .25). However, a repeated measures ANOVA yielded
significant differences in looking times as a function the trial (F(5, 935) = 4.35, p =
33


.01), indicating that overall response strength decreased as a function of repeated
speech segment presentations.
Looking times at the slide presentations were examined to identify any
differences in responding as a function of the number of slide presentations or as a
function of the BDI category of the mother who produced the speech segment.
Looking times during the slide presentations did not differ as a function of the BDI
category of the mother who produced the speech segment (F(10, 367) = .50, p
=.89). However, there were significant decreases in looking times as a function of
trials for the slide presentations as revealed by a repeated measures ANOVA (F(5,
185) = 2.93, p = .01). The significant differences in looking times as a function of
the trial for both the voice and face presentations suggest that the infants
habituated somewhat to the task2.
Summation Phase
Summation tests involved four 10-s presentations of a black-and-white
checkerboard pattern, with the speech segment from the pairing phase
compounded with the first and fourth checkerboard patterns. Prior studies have
indicated that only forward pairings of ID speech segments and faces yield
significant positive summation (as opposed to a backward control condition, see
Kaplan et al. 1996; Kaplan et al. 1997) and therefore significant positive
summation is interpreted to result from an associative process. Table 3 presents
34


the mean looking times during the four test trials as a function of the BDI category
of the mother who produced the speech segment. Difference scores were obtained
by subtracting the means of the first and fourth trials from the means of the second
and third trials. The higher the difference score the more associative learning was
assumed to have occurred. Consistent with previous findings, mean difference
scores were higher in the low- and mid-BDI conditions than in the high-BDI
condition. Mean difference scores for the infants who heard speech samples from
mothers in the low-, mid-, and high-BDI categories were 0.72 s (SD = 2.28), 0.8 s
fSD = 1.85), and 0.64 s fSD = 2.14), respectively. One sample t-tests revealed
that mean difference scores for the low- and mid- BDI categories were
significantly different from zero (t(79) = 2.81, p = .01, and t(79) = 4.10, p < .01).
In contrast, the mean difference score for the high-BDI category was not
significantly different from zero, t(29) = 1.62, p = 12). However, a one-way
ANOVA revealed no significant differences among mean difference scores as a
function of the BDI group of the mother who produced the speech sample, F(2,
187) = 0.16, p = .86. When BDI score was analyzed via linear regression against
mean difference score, the trend was similarly non-significant, r^lS) = 0.01, p >
.67).
Unexpectedly, the RADS scores were significantly and positively
correlated with the mean difference scores (if(17) = .30, p =.02). This correlation
35


was unexpected given that difference scores were predicted to decrease as
reported symptoms of depression increase. However, the RADS was not
significantly correlated with any of the other variables in the study including BDI
scores (i^(17) = .10, p =.22). The BDI was chosen as the primary tool for analysis
because it has been shown to be a more sensitive measure of depression in an
adolescent sample (Atlas and DiScipio, 1992) and because it facilitated
comparisons between the adult and adolescent results.
Also contrary to expected outcomes, there was no significant association
for the mean Fo change for the gorilla utterances and the mean difference score
(1^(18) = 0.06, p =.30). A multiple regression analysis was run to identify the
extent to which the independent variables (BDI score of the mother who produced
the speech sample, mean F0 change for the gorilla portion of the speech segment
and mean Fo for the gorilla portion of the speech segment) accounted for the
variance in the difference scores. All independent variables were entered into the
equation resulting in R2 = .16, p = .77 and none of the variables independently
accounted for a significant proportion of the variance in the summation scores
mean F0 for the gorilla utterances.
Although difference scores did not significantly vary as a function of the
BDI score of the adolescent mother who produced the speech sample, difference
scores were lower among infants in the current study tested with speech samples
36


produced by non-depressed mothers than they were in the comparable study with
non-depressed adult mothers (Kaplan et al., in press). The mean difference score
for infants tested with non-depressed adolescent mothers ID speech was 0.40 s
less than that for infants tested with non-depressed adult mothers ID speech, a
trend that narrowly missed attaining conventional levels of significance as assessed
by a one-way ANOVA, F(l, 303) = 3.26, p < .08.
37


CHAPTER 4
DISCUSSION
Adolescent mothers varying on self-reported symptoms of depression
demonstrated differences in vocal quality during a structured play interaction with
their two- to eight-month-old infants. Adolescent mothers who reported relatively
fewer symptoms of depression displayed significantly more mean Fo modulation in
the gorilla portions of their speech segments, while adolescent mothers who
reported relatively more symptoms of depression exhibited less mean Fo
modulation. In addition, the mean F0 change during the gorilla portion of the
speech segment was significantly associated with the overall mean Fo of the
gorilla portion of the speech segment. Speech segments with greater F0
modulation tended to have a higher overall mean Fo. However, there was a non-
significant association between overall mean Fo and BDI scores reported by the
mother who produced the speech segment, possible implications of which will be
addressed below. Frequency modulation (Femald, 1984; 1985; Kaplan et al. 1992)
and mean Fo or pitch (Femald and Kuhl,1987) are both hypothesized to be
important acoustic determinants of the effectiveness of ID speech.
As stated previously, depressive symptoms have been associated with
changes in the F0 modulation of ID speech (Kaplan et al., in press). Frequency
modulation and other qualities of ID speech, in turn, are hypothesized to be
38


important determinants of the ability of ID speech to promote attention, arousal
and consequently associative learning in infants (Cooper and Aslin, 1994; Femald
and Kuhl, 1987; Kaplan et al., 1995). On this theoretical foundation, significant
associations between BDI and mean Fo change, mean Fo change and difference
scores, and BDI and difference scores were expected. However, no significant
associations were identified between BDI scores of the mother who produced the
speech sample and the difference scores of the infants tested with those speech
segments. Significant conditioning (mean difference scores significantly different
from zero) was found to occur in the low and mid- BDI categories but not the high
BDI category. This result may be taken to suggest that the ID speech produced by
mothers in the high BDI category failed to promote associative learning, except
that the number of infants in the high BDI condition was small, resulting in low
statistical power, and there was no significant difference in difference scores as a
function of the BDI category. The fact that difference scores for non-depressed
adolescent mothers were lower than those for non-depressed adults tested under
nominally very similar conditions (Kaplan et al., in press) suggests that the absence
of an effect of maternal BDI score on infant learning score may be due to a floor
effect. This floor effect, in turn, could be attributed to the relatively lower
frequency modulation in adolescent vs. adult mothers gorilla utterances.
39


Some theorists have argued that the use of ID speech is, if not universal,
ubiquitous. Indeed, evidence shows that parents in many different cultures, with
different levels of experience with infants and even older siblings of infants adopt
the ID speech register in addressing young infants (Femald, 1984). Yet, significant
acoustic differences were identified between adult and adolescent mothers here.
Adolescent mothers had significantly higher mean Fo than adult mothers regardless
of the BDI score of the mother who produced the speech segment. In addition,
the proportion of unmodulated gorilla utterances was higher for adolescent
mothers than adult mothers. The increased proportion of unmodulated gorilla
utterances and lower mean Fo change exhibited in the speech segments of
adolescent mothers suggests a deficit in ID speech either due to adolescent status
or to any number of correlates of adolescent mother status including low SES,
psychosocial stress or depression.
Differences in acoustic qualities between adult and adolescent mothers
would suggest that differences in conditioned attention of infants tested with those
speech segments would also exist and, in fact, this was the case. The difference
scores of infants tested with ID speech segments produced by adolescent mothers
were lower (narrowly missing conventional statistical significance) than those
infants tested with the ID speech of adult mothers. Replication of this result in
future studies which control for race and SES could have powerful implications for
40


our understanding of the genesis of cognitive deficits that some children of
adolescent mothers exhibit (Furstenberg, 1989; Moore, 1986; Moore, Morrison
and Greene, 1997).
Nevertheless, comparisons between the adult and adolescent data in this
study must be approached and interpreted with caution. First, the adult sample of
data was collected for a previous study with a distinct method of recruitment and
was not originally intended to be compared with an adolescent sample. Secondly,
the racial distribution and the levels of SES are disparate. The majority of the
adult sample were non-Hispanic whites and primarily from middle-class homes
while the adolescent sample was racially mixed and predominantly from lower SES
homes. In past studies where differences in SES were statistically controlled,
differences between adolescent and adult mothers virtually disappear (Klerman,
1993).
In fact there are interesting similarities in the parenting styles of mothers,
from low SES homes and the parenting styles of adolescent mothers. Adolescent
mothers tend to be less verbally stimulating (Culp, Applebaum, Osofsky & Levy,
1988; Field et al., 1990; Lester & Zeshin, 1978), less responsive (Me Araney and
Lawerence, 1985) and tend to be more punitive and authoritative in their parenting
styles than the comparison group of adult mothers (Camp, 1995; Field et al. 1980;
Kissman, 1988; Reis & Hertz, 1987). In studies examining the parenting behavior
41


of adult mothers from low SES homes the mothers provided less cognitive
stimulation, were less responsive and tended to be more punitive and dominating
(Bee et al., 1982; Clarke-Stewart & Apfel, 1978; Siegel, 1982; J. Smith et al.,
1997).
Similar cognitive and emotional sequeale are also observed for the children
of adolescent mothers and adult mothers in low SES groups. Cognitively, children
with adolescent mothers and children from low SES homes show cognitive deficits
beginning in the preschool years continuing throughout their school years and have
higher failure rates in school (Duncan, Brooks-Gunn, and Klebanov, 1994; Liaw
and Brooks-Gunn, 1994, Smith et al., 1997). Emotionally and behaviorally,
children from low SES homes and whose mothers were adolescents at the time of
their birth are similar also. Children from these homes demonstrate more
behavioral problems including higher levels of aggression and lower levels of
impulse control (Achenbach, Verhurst, Edelbrock, Baron, and Akkerhuis, 1987;
McLoyd, Ceballo, and Mangelsdorf, 1996).
One explanation for the similarities that are observed among adult mothers
from low SES groups and adolescent mothers may be the increased levels of stress
that mothers from both groups are likely to experience. Stressful life events and
conditions have been shown to decrease the stimulation provided by the caregiver
in the home environment (Sameroff, Seifer, Barocas, Zax & Greenspan, 1987).
42


Less stimulating home environments have, in turn, been linked to a decrease in IQ
in children (Brooks-Gunn et al., 1995; Bradley et al., 1989; Bradley, Whiteside,
Mundffom, Casey, Kelleher and Pope, S., 1994). These studies highlight the
importance of identifying the role of SES and life stress when drawing conclusions
about differences that are observed between adolescent and adult mothers and
their children. If low SES or stressful life events are found to play a significant role
in the quality of ID speech produced by a mother, it may offer significant insight
into cognitive and verbal deficits that some children living in low SES homes
exhibit.
There are also notable complications in the interpretation of the adolescent
data due to stark ethnic differences. To begin, there are significant differences
among the acoustic qualities of the speech sample as a function of the race of the
mother who produced the speech sample. The speech samples produced by non-
Hispanic white mothers were significantly more modulated than the speech
samples produced by either African-American or Hispanic mothers. The mean Fo
and mean F0 change were also significantly higher for the voices of non-Hispanic
white adolescent mothers than either African-American or Hispanic mothers. In
one respect the racial differences in ID speech are surprising given the universal
nature of ID speech. Also, given the large differences in acoustic qualities one
would expect large differences in the difference scores of the infants as a function
43


of the race of the mother who produced the speech segment. However, this result
was not found. Racial differences have been identified in studies on the
interactions of Cuban and African-American adolescent mothers. (Field et
al.1990). Field et al.(1990) found that Cuban adolescent mothers tended to be
more indulgent, more socially stimulating and tended to vocally stimulate their
infants more than African-American adolescent mothers who tended to be more
restrictive, punitive and less vocally stimulating. Socioeconomic status was
controlled in the Field et al.(1990) study suggesting that their results were indeed
due to cultural differences.
In the present study the RADS was utilized as a second self-report measure
of depression. As mentioned previously, higher scores on the RADS are
indicative of a greater number of self-reported depressive symptoms. Thus, the
RADS and the BDI were expected to correlate positively with each other and
correlate negatively with the difference scores of the infants tested with the speech
segment produced by the mother completing the self-report measures. Yet, the
conditioning scores of the infants were positively and significantly correlated with
the RADS scores reported by the adolescent mothers. This result is difficult to
interpret. One possible explanation for this result may be the disparity between the
ethnic composition of the sample in the initial validation study for the RADS and
the ethnic composition of the sample in the present study. Ethnic distribution for
44


the initial validation study of the RADS was 75.8% white, 20.6 % African-
American and 3.6% other minority group membership (Reynolds, 1987) whereas
the racial distribution for the present study was 42% non-Hispanic white, 37%
Hispanic and 21% African-American. The RADS was not significantly correlated
with any of the other variables in the study, making further interpretation of this
result ambiguous and unreliable.
The role of stress in the mothers life is also a factor yet to be explored. If
floor effects account for the absence of an effect on infant difference scores of the
>
maternal BDI scores, it may suggest that high levels of stress common among
adolescent mothers is actually a key factor influencing changes in the quality of ID
speech. Therefore examining the ID speech of adult mothers who are distressed
may indicate whether the changes in ID speech are specifically due to depression
or whether the changes in the quality of ID speech are actually due to correlates of
depression.
The results of the present study show that there are acoustic differences in
the ID speech of adolescent mothers who report various symptoms of depression.
However, there were no differences in the conditioning scores of the infants as a
function of the BDI score of the mother who produced the speech segment. Less
F0 modulation in the ID speech of adolescent mothers in this study may suggest
that there is a floor effect and the ID speech of adolescent mothers as a group is
45


less modulated in general. Differences in the conditioning scores between
adolescent and adult mothers may suggest that the ID speech of the adult mothers
promotes infant associative learning better than the ID speech of the adolescent
mothers. However, reasons for these differences are unclear due to the disparity in
the ethnic and SES between the two samples. Further research with matched
samples would be extremely valuable to the understanding of ID speech, mother-
infant interactions and the influence of adolescent motherhood.
46


300
250
200
150
100
50
i i i i i i ..................... i i i i i i i i i i
2 3 4 5 6 7 8 9 10111213141516171819 20 21 22 23 24 25
BDI SCORE


Table 1
Fundamental Frequencies (FnS 'l and Changes in Fn (AFnsI for Gorilla Utterances
First Gorilla Second Gorilla Third Gorilla Overall Mean
BDI F0 AF0 F0 AF0 F0 AF0 F0 AF0
2 368 258 327 161 329 239 341 219
7 400 324 456 233 464 317 440 291
7 374 208 370 285 429 170 391 221
7 280 36 434 106 336 89 350 77
7 286 95 373 102 369 366 343 188
8 297 78 352 77 244 122 298 92
9 492 158 448 81 402 127 447 122
9 226 60 290 118 211 75 242 84
M 340 152 381 145 348 188 357 162
11 260 40 311 177 311 99 294 105
12 200 131 269 134 238 127 236 131
12 303 134 347 63 295 56 315 84
12 492 145 464 93 439 205 465 148
12 428 242 526 288 336 88 430 206
12 264 204 281 116 228 82 258 134
13 271 129 308 106 183 107 254 114
15 426 247 389 121 458 107 424 158
M 331 159 362 137 311 109 335 135
16 344 131 375 134 222 127 314 131
21 347 54 485 86 339 171 390 104
25 256 18 271 25 250 91 259 45
M 316 68 377 82 270 130 321 93
48


Table 2
Summary Temporal. Frequency and % Unmodulated Pitch Contour
Measures for Gorilla Utterances
Adolescent Adult
BDI Rep Duration Mean (s) F0(Hz) AF0 (Hz) % Flat Duration (s) Mean F0(Hz) AF0 (Hz) % Flat
1 0.47 340 152 50 0.50 247 148 43
Low
(0-9) 2 0.42 381 145 63 0.52 297 143 29
3 0.63 348 188 50 0.51 299 215 0
M 0.51 357 162 54 0.51 281 169 24
1 0.45 331 159 63 0.47 329 172 33
Mid 2 0.41 362 137 75 0.51 318 141 67
(10-15)
3 0.39 311 109 88 0.51 324 141 33
M 0.42 335 135 75 0.50 324 152 44
1 0.57 316 68 100 0.55 297 156 57
High 2 0.49 377 82 100 0.54 290 139 57
(16-25)
3 0.56 270 130 67 0.53 269 117 86
M 0.54 321 93 89 0.54 285 137 67
49


Table 3
Mean Looking Times During the Four Test Trials Across Conditions
BDI n m/f Days Old Trial 1 Trial 2 Trial 3 Trial 4 D.S.
2 11 8/3 117.82 7.22 5.93 4.71 4.45 0.51
7 11 5/6 120.55 6.76 7.05 5.35 6.33 0.40
7 11 3/8 121.36 8.34 8.13 8.16 8.22 0.14
7 11 5/6 121.36 5.52 4.10 3.50 4.65 1.35
7 10 5/5 118.30 6.44 5.51 5.43 6.78 1.19
8 12 6/6 123.00 7.25 6.58 6.86 7.41 0.64
9 13 6/7 119.46 8.17 7.51 6.22 6.39 0.41
9 11 5/6 122.64 7.15 6.37 5.46 7.00 1.16
1= 90 43/47 M 120.56 7.11 6.40 5.71 6.40 0.72
11 12 7/5 120.46 8.57 6.42 5.80 7.35 1.74
12 13 6/7 118.77 7.67 7.12 6.57 7.91 0.95
12 10 4/6 122.10 7.35 7.34 6.69 8.28 0.93
12 11 4/7 116.18 7.41 6.53 5.52 5.76 0.51
12 11 5/6 117.46 7.18 7.53 6.19 7.43 0.50
12 10 4/6 122.50 7.16 6.14 6.43 7.29 0.93
13 12 7/5 125.08 7.60 6.80 6.44 6.95 0.66
15 10 6/4 116.67 8.34 7.65 6.54 7.34 0.75
2= 79 37/42 M 120.36 7.56 6.84 6.23 7.28 0.85
16 11 5/6 121.55 7.12 5.54 5.25 5.37 0.81
16 13 9/4 121.08 7.59 5.89 5.63 5.47 0.77
25 11 6/5 119.55 6.42 5.55 5.27 5.01 0.31
1= 45 26/19 M119.71 7.37 6.16 5.67 5.80 0.63
50


Figure Caption
Figure 1. Mean frequency change during the gorilla portion of the speech
segment as a function of the BDI score of the mother who produced the speech
sample.
51


Footnotes
1. Speech served here as CS, but also has UCS properties.
2. Habituation, as a result of the repeated presentation of the face slide, occurred
during the pairing phase of the conditioned attention task (Kaplan, Werner and
Rudy, 1990). Although this finding is inconsistent with previous studies where
there were no significant differences in looking times during the pairing phase
(Kaplan et al., 1996; Kaplan et al., 1997; Kaplan et al., in press), a significant
decrease in the looking times during the slide presentations may be a result of the
repeated exposure to the same stimulus, decreasing in the arousal of the infant
leading to habituation (Kaplan et al., 1990). However, this effect was not found to
be a function of the BDI score of the mother who produced the speech sample.
3. Femald and Simon (1984) the prosodic patterns of ID speech were
characterized by Fo excursions averaging 13 semitones/s which is roughly equal to
half and octave which is roughly equal to 150 Hz.
52


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